1. Field
Disclosed herein is a current sensor arrangement for measuring currents in a primary conductor over a wide measurement range.
2. Description of Related Art
For proximity and thus potential-free measurement of the strength of an electrical current in a conductor, on the one hand so-called direct-imaging current sensors are known which detect the magnetic flux which has been caused by the current, for example by means of a Hall sensor in a slotted magnetic circuit, and generate a signal which is proportional to the current strength. These sensors are very economical, but have relatively low accuracy. Direct-imaging current sensors are so-called open-loop current sensors which do not contain a closed control circuit.
Furthermore, so-called closed loop current sensors are known in which an opposing magnetic field of the same size as the magnetic field of the current to be measured is continuously generated using a closed control circuit, so that complete magnetic field compensation continuously occurs, and the magnitude of the current to be measured can be deduced from the parameters for generating the opposing field. Closed loop current sensors therefore belong to the class of compensation current sensors.
One special type of compensation current sensors which, however, do not contain a closed control circuit are flux gate sensors embodiments of which, for example, are described in document DE 42 29 948. Since hysteresis errors are avoided in these current sensors, they are suitable for precise current measurement in a wide dynamic range from a few milliamperes to roughly one kiloampere.
Flux gate sensors do not enable continuous current measurement, but the output signal of the sensor is a periodic signal which is sampled at certain sampling times. The sample values represent the current in the primary conductors (primary current) at the discrete sampling instants.
When the frequency of the primary current is similar or equal to the sampling frequency, in the sampled output signal of the sensor, as a result of aliasing effects, beats become visible. These beats lie in a frequency range which is important for current measurement, and thus clearly disrupt the measurement. This disruption can go so far that, in many cases, meaningful current measurement becomes impossible, as a result of which the domain of practical application of the current sensor is greatly limited. Furthermore, these current sensors generally have recurring time intervals in which the current cannot be measured at all.